Is Duty Payable on Dilapidated Property?
It really depends on whether you are looking at a fixer upper or it is uninhabitable. You need to check the rules. Duty is a personal TAX. It is a self-assessment. It is not your agent's (conveyancer's) responsibility to get it right. You pay the penalty. The Revenue can investigate months after completion. Fraud of the Revenue is a criminal offence.
Check out the provisions online.
• Welsh Revenue Authority for Wales
• HMRC for England